This invention relates to an improvement in an internal combustion engine that has solenoid-controlled cylinder valves.
Historically, the timing and lift of the cylinder valves of an internal combustion engine have been rigidly defined by the design of its camshaft, and that design has typically been a compromise of numerous factors. The advent of solenoid-controlled hydraulic controls for controlling cylinder valve timing and lift enables these parameters to be varied in ways that allow them to be more or less optimized to suit the particular operating needs of the engine as those needs change in accordance with different operating conditions. This capability is especially advantageous when the engine is used as the powerplant of an automotive vehicle.
The present invention arises through the observation of unanticipated, and sometimes sporadic, aberrations in the operation of such solenoid-controlled hydraulic controls and the ensuing recognition that such irregularities are a consequence of uncontrolled factors like hydraulic fluid viscosity, battery voltage, and manufacturing tolerances, to mention a few. Accordingly, the invention provides a solution to this predicament by means of a novel closed loop control system that functions to nullify the undesired effects of certain inherently uncontrolled factors such as those just mentioned. In a general way, the practice of the invention occurs in the following manner. The actual lift of a cylinder valve is monitored by a lift sensor that is coupled to an electronic valve controller by a lift signal processing circuit, and the electronic valve controller issues a control signal that is calculated to secure as faithful correspondence as possible of this lift signal to a command signal that the electronic valve controller receives from an electronic engine management controller. The processing circuit functions to disclose to the electronic valve controller the actual opening and closing instants of the cylinder valve in a manner that amounts to the sensor being calibrated to zero each time that it closes. This allows a relatively inexpensive sensor such as a Hall device to provide sufficient accuracy. In any given engine, the invention may be embodied in the intake valves and/or the exhaust valves.
The foregoing features, advantages, and benefits of the invention will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawing which presents a preferred embodiment of the invention according to the best mode contemplated at the present time for carrying out the invention.